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About 1.47 percent of foreign travelers with visas overstayed their expected departure.

Hundreds of thousands of foreigners overstayed their visas in fiscal 2016, but new biometric data collection efforts could help cut that number, according to the Homeland Security Department.

More than 700,000 overstayed their expected departure date in 2016, a DHS report notes. Visa overstay data includes temporary workers, tourists visiting for pleasure, and students, among other groups who entered the country through air and sea ports.

Of about 50,427, 278 people processed at those ports—about 1.47 percent—missed their departure date, and about 1.25 percent were suspected to have stayed in the country with no recorded departure, the data show. The rate is much higher for student and exchange visitors: of about 1,457,556, about 5.48 percent overstayed, DHS concluded.

The department is working on a biometric system that would allow agents to compare the facial, fingerprint or iris scans of travelers exiting the country to those who entered it. It has already a pilot at Atlanta's Hartsfield-Jackson International Airport; Customs and Border Protection has partnered with an airline to test out a biometric system that would better confirm the identity of departing travelers. President Donald Trump also recently signed an executive order directing DHS to deploy a biometric exit system.

DHS has drawn criticism from watchdogs who warn technological struggles could prevent the department from identifying all overstays. For instance, DHS' Office of the Inspector General pointed to Immigration and Customs Enforcement’s fragmented IT systems as a major stumbling block; in some cases, ICE personnel must consult up to 27 separate databases to establish whether foreign travelers have overstayed their visas or whether they're national security threats, according to a recent report.

OIG concluded earlier this month the U.S. has at least 1.2 million visa overstays in a backlog. A better biometric system would let DHS collect its own data, instead of relying on commercial airline data to compare departing travelers' identities to those who entered the country, the report said.

DHS' biometric exit systems are still nascent, the Government Accountability Office concluded earlier this year—and as a result, the department doesn't even have a full picture of who is overstaying their visas. Overstays could pose “significant homeland security risks,” GAO wrote in that report; at least five out of the 19 Sept. 11 hijackers were overstays.

GAO concluded then CBP faced significant challenges in planning and staffing that might prevent it from deploying a full biometric exit system at one airport by 2018.